Due to the time and expense associated with full-scale structural fatigue testing, test laboratories are typically under pressure to reduce their operating expenses and to produce results more quickly. An increase in the cycling rate of a full-scale fatigue test may lead directly to lower laboratory costs and may provide test results sooner. For example, in the aircraft industry, significant potential savings may be realized in retrofit and fleet repair costs if structural fatigue test results can be provided more quickly.
Cycling rate may be a function of many parameters. One parameter that is particularly critical is the accuracy of the applied test loads. Typically there is a required spectrum severity that must be maintained. As the cycle rate increases, there is a potential for the loads to be applied with less accuracy, reducing (or increasing) the severity of the applied spectrum. A current process to evaluate the tested spectrum severity involves applying a significant portion of the spectrum while recording the load feedback and strain gage output. These data are then evaluated, which may take days or weeks before results are known.